1. Field of the Invention
This invention relates to a circuit which is directed to the image conversion of digital images inputted from imaging means such as an area sensor and digital images formed by a computer, or the like.
2. Description of the Prior Art
Maximum/minimum value conversion in a proximity region in multilevel digital image processing is a relatively effective technique as one of image conversion techniques because it can erase a specific region which is brighter than its surroundings by minimum value conversion in the case where a pixel value represents luminace, for example.
In accordance with the conventional technique, however, a plurality of conversion stages each consisting of a delay circuit, a plurality of proximity value hold circuits of a small scale matrix form such as 3.times.3, a maximum value selection circuit for selecting the maximum value among the values held by the proximity value hold circuits and a proximity center value conversion circuit for converting a proximity center value by the signal outputted from the maximum value selection circuit are arranged in series, conversion of a small scale proximity region is effected at each of these stages while conversion of a large proximity region throughout a series of the stages is effected, or conversion is repeatedly made at a single stage to obtain the same conversion result as above.
In order to make large proximity region conversion by repetition of small scale conversion such as 3.times.3 in the conventional circuit, however, an extremely long conversion time is necessary, and if a circuit capable of large proximity region conversion or a large number of small scale conversion circuits are connected in series in a plurality of stages in order to shorten the conversion time, the circuit becomes inevitably great in scale.